The present invention relates to a coupler and, more particularly, to a coupler for articulated convertible rail-highway vehicles which are adapted to operate on highways as conventional semi-trailers as well as on railway tracks in an articulated train mode.
Couplers for connecting articulated convertible rail-highway vehicles are known generally as for example is shown in U.S. Pat. Nos. 2,925,791, 4,202,454 and 4,311,244. Couplers which are similar to couplers for convertible rail-highway vehicles are also known as for example is shown in U.S. Pat. Nos. 1,848,956, 2,677,472, 2,812,726, 2,816,517, 2,843,056, 2,963,986, 3,396,673, 3,399,631, 3,476,040, 3,646,604, 3,716,146, 4,258,628, 4,336,758, 4,456,133 and 4,593,828.
The provision of couplers for convertible rail-highway vehicles presents a number of considerations that are not necessary or at least not imperative when providing couplers for railroad cars. In particular, couplers for articulated convertible rail-highway vehicles must not interfere with the conventional tractor-trailer geometry and must permit utilization of the full cubic capacity of the semi-trailer within legal height and length limitations. For example, the coupler must be able to support the weight of the front of the following vehicle in an articulated configuration without high structural bending stresses. Thus, such a coupler must be strong enough to withstand train tension and compression forces of 400,000 lbs or more. However, the coupler must be shallow so that it can easily pass over the fifth wheel of an associated tractor while not extending above the floor of the trailer body.
Such a coupler should also enable automatic coupling of first and second vehicles so that an operator need not be present during the coupling operation. It would also be desirable to provide a coupling assembly which will gather the vehicles together when the couplers are slightly misaligned before coupling while providing slack free, i.e. tight, connection so that loads and forces can be transmitted about all axes.
A further advantageous characteristic of a coupler for articulated convertible rail-highway vehicles would be a structure which permits roll, pitch and yaw motions to be taken at a point between the end faces of the coupled vehicles so that the vehicle frames are not unduly stressed while operating in the rail mode. It would further be desirable to provide couplers that are capable of providing at least limited shock absorption in the coupler mounting to attenuate longitudinal shock loads during coupling operations and/or when a semi-trailer is coupled to a tractor for operation in the highway mode. Yet another desirable characteristic would be the ability to automatically connect air brake lines or other service or power lines between vehicles so that no separate coupling operation is required.
While couplers for articulated convertible rail-highway vehicles are known, a coupler exhibiting all the above-mentioned advantageous characteristics has not previously been developed. For example, in U.S. Pat. No. 4,202,454 a coupling assembly is shown which includes a female coupler and a male coupler. The female coupler is provided in the rear sill structure of a convertible rail-highway vehicle and includes a pin which passes through a corresponding aperture provided in the male coupler so as to lock the male coupler within the female coupler. The coupling assembly of this patent permits relative roll, pitch and yaw motions between the coupled vehicles by providing a spherical bearing within the male coupler through which the locking pin passes. Thus, in this coupling assembly, relative motion of the vehicles is carried within the rear sill structure of the forward vehicle. U.S. Pat. No. 4,311,244 is substantially similar to the '454 patent but further includes an actuating pin which is engaged by the male coupler during the coupling operation and releases the locking pin so that it may lock the male coupler within the female coupler.
It has been found that the foregoing couplers are not entirely advantageous when utilized to connect convertible rail-highway vehicles. More particularly, the '454 patent requires that an operator be present to move the locking pin both into and out of engagement with the male coupler. Further, both these couplers, while permitting relative movement between the vehicles, carry relative movement within the rear sill structure of the leading vehicle and, thus, the male coupler element is subjected to a great deal of stress.